It is well known that when an ink-jet pen is stored in an inactive state, the nozzles often clog with crusted ink components. This constitutes the pen recovery problem.
There are many recovery algorithms that help to alleviate the problem, for example, the ink firing chamber of the pen can be heated and the inks can be repeatedly spit in a spittoon, with intermittent wiping of the pen (sometimes, with a solvent such as glycerol or polyethylene glycol (PEG)). Alternatively, the pen can be actively primed by a pump. Also, adding co-solvents (humectants) and surfactants helps to slow down crusting of ink components by reducing evaporation, such cosolvents and surfactants occasionally even forming a soft gel plug of the solvent at the nozzle. All of these ways of dealing with the pen recovery problem are either time-consuming, not consistently effective or both.